EPOW - Ecology Picture
of the Week

Each week a different image of our
fascinating environment is featured, along with a brief explanation written
by a professional ecologist.

23 February - 1 March 2009

Click on images for larger versions

Glacial
Shrinkage in the Andes

Volcan Lanin, Andes Mountains
Argentina, South America

Credit & Copyright: Dr. Bruce G.
Marcot

Explanation: Towering
some 12,388 feet (3,776 meters) into the clouds is this massive extinct
volcano that straddles Argentina and Chile in the southern Andes Mountains of
South America at nearly 40 degrees south latitude below the
equator.

Volcan
Lanin itself is actually a composite of four major geological periods of
eruption and a number of layers, and is termed a compound
stratocone.

But
although the eruptions have subsided -- with the last eruption in the Holocene
-- the ice is alive with daily meltwater. The glaciers are melting.

Just
a few decades ago,
a glacier filled the trough
in the lower part of this
photo
of the slopes of
Volcan Lanin.

Studies have shown significant "retreat"
of glaciers in the Andes Mountains in recent decades, apparently because
of the warming of the atmosphere and lessening precipitation. Research
on a nearby volcano, Volcán Mocho-Choshuenco, showed a 40% reduction in the
area of glacier cover between 1976 and 2003.

Snow, ice, and glaciers on
Volcan Lanin are melting.

When
glaciers melt, there is often a positive feedback effect leading to even
faster melting. The melting first uncovers darker-colored rock which
then absorbs sunlight and heat far more effectively than did the reflective
white of the ice and snow, so the land warms even
more quickly. In these photos of Volcan Lanin, compare the dark
exposed slopes to the white of the glacial ice.

Melting of glaciers can have serious
effects on humans. Mountain glaciers provide an ecosystem service
of providing fresh water to people in many parts of the world, especially
the tropics. Loss of glaciers in the Andes could threaten the loss
of water to 30 million people. In
one report, the Chacaltaya Glacier in Bolivia has nearly disappeared
completely.

Melting of alpine glaciers can have many
ripple effects.
In the southern Andes Mountains, changes in climate,
water runoff, cloud formation, precipitation, and temperature
could drastically alter local vegetation and habitats for plants and animals.
Shown here is a stand of "monkey
puzzle trees" in which I found a
flock of Austral Parakeets feeding on the seed cones. How
changes in this vegetation might affect the trees, birds, and other wildlife
is unknown.